As advised by the previous owner, I have been checking the overflow tank which seems to be losing coolant over time. It was full a couple of days ago when I bought the car, however it's now down to about half way.

No oil in water, no water in oil.

No smoke.

No leaks by the looks of things.

What could this mean?

 

Overflow or expansion tank?

The overflow can fluctuate, as long as the expansion tank on the left stays full you should be ok. If your concerned get it sniff tested and pressure tested 👍

 

It's the overflow, on the right as you open the bonnet.

I just realised I only looked when cold, and after looking when warm it's back up to the full line. Nevermind, kn*b alert..

 

Should only fluctuate due to being hot or cold.
When your engine is stone cold in the morning make sure it's top up to the full line.

Then keep an eye on it over the next few days, If the level is below the max line again when the engine is cold then there is a problem.

Obviously when the engine is hot it will be above the max line but should return to full over night as the engine fully cools.

If your finding there is a loss of coolant first things you want to check is the condition of all your coolant hoses and radiator for any sign's of a leak, could be very slight dribble when the system is under presure when hot.

If that's all ok then it would be wise to have a hydrocarbon test done to rule out the possibility of a head gasket problem.
I've had a head gasket fail on one of my Impreza's and the only symptoms I had was a watery noise from behind the dash due to air lock in the heater matrix, and bubbles appearing in the expansion bottle after hitting full boost a few times.

 

Is this the overflow tank you're talking about? This wouldn't be full when fully cold would it?

 

Yes the coolant in the expansion tank aka overflow should be on the full line when cold.
When the car gets hot the coolant will expand and go above the line.

After the car has fully cooled down the coolant should return back to the full mark.

 

I thought these were two separate parts in the car?

 

Yes Headder tank on the left hand side when looking at engine by intake manafold should be full. This is the highest point in the system and should be full to the brim when cold.

The white plastic expansion bottle in the right hand of the engine bay should also be on the full line when the engine is cold.

When hot the coolant will expand in the plastic bottle over the full line. And return when cold.

 

I feel like you're wrong about the overflow/expansion tank being full when cold. The overflow tank is called an overflow/expansion tank for a reason. Surely you wouldn't want this 'full' when the car is cold. There's a reason why it's full when the car is hot.

 

No..... Look in your owners manual.

 

There full means the coolant is at correct level!

There is plenty of space for it to expand into above the full mark.

 

Overflow should be on full when cold and will raise when warm and return to full when cold as said above, header tank should always be full!!!

 

Apologies, you are right. Just had a look in the Owners' manual.

I guess I haven't checked when fully cold yet, but I will do tomorrow morning. I've seen some people just fill it to the low mark, so maybe that's where it's been filled to anyway. I will double check in the morning.

 

You should also check the rubber seals in the header tank and radiator tank caps for perishing.

If you're 100% sure there are no leaks this could be an early sign of HG failure unfortunately.

 

Nope, all is well. Car has been left for 3 hours and it's just below full. I think I was being blind before by just using the outside as a reference as to how full it is, when really I should have looked inside.. Header tank is fine also sorry guys, ive wasted your time

 

The block will still have heat in it after 3 hours. Make sure it's on the full mark before you set off in the morning.

 

Inturbo - no! I was content knowing there's no issue! Now I won't be able to sleep.. Haha, thanks for the advice guys, appreciated.

 

Lol, in the morning when stone cold, check both tanks, give the expansion tank by the radiator a wipe as it could be filthy on the outside. I like to keep it clean and shine a torch down through the hole at the top after flipping off the yellow cap.


As said, from stone cold the header tank - to your left should be fill to the brim, and the expansion tank to your right should be on full - or halfway between low and high markers is ok.


Good shout from Norman Dog, wouldn't hurt to get new caps aswell. The seals do perish in time. Just be sure to put (all when stone cold again) the cap with the ears onto the header tank, and the round cap onto the radiator. Just do one cap at a time though.
Heard stories of these two caps going on the wrong items....not good!

 

I would get it all checked out first , sniff test plus fill it yourself and see if you get issues , it sounds like hg but confirm it first, no point spending loads of money if you don’t need too , other option is contact seller ? , the pressurised caps can fail and cause issues so worth repacking them first , the symptoms i always had ... 3 rebuilds later 😕 was the non pressured expansion tank on the rad would not drain back to the system plus excessive bubbles in the same tank , other good builders if it’s bad news are subaru4u and richard at Fb tuning

 

ignore about post , i changed settings so it did not bring up old posts it’s clearly not worked 😕